Fast clock generator and clock synchronizer for logic derived clock

Abstract

A programmable device includes a circuit for generating an asynchronous logic derived clock signal derived from one or more of a number of input signals. Circuits for synchronizing the asynchronous logic derived clock signal to a reference clock signal are coupled to the circuit for generating the asynchronous logic derived clock signal. The circuits for synchronizing generate a synchronized logic derived clock signal from the asynchronous clock signal and a reference clock signal. The programmable device further includes a circuit for suspending a clock signal. In one embodiment, a logic derived clock signal is generated and synchronized with a synchronous clock signal. In synchronizing the logic derived clock signal an intermediate signal is generated during a first clock cycle of the synchronous clock signal and is combined with the synchronized logic derived clock signal during a second clock cycle of the synchronous clock signal to produce a suspendable clock signal. The suspendable clock signal may be gated off in response to an input signal having a minimum duration of at least two clock cycles of the synchronous clock signal.